Joint relay selection and power allocation with QoS support for cognitive radio networks

In this paper, we consider the problem of joint relay selection and power allocation in a cognitive radio (CR) network, where a secondary user (SU) source communicates with a secondary access point (AP) assisted by a set of SU relays. Each SU in this set not only acts as a potential relay but also has its own data transmission requirement. Keeping the interference to the primary user (PU) below a specified limit, we propose an optimal scheme with quality of service (QoS) support. On the premise of meeting the minimum transmission rate requirements of all SUs, the goal of the proposed scheme is to maximize the weighted sum rate of the network under transmission power and energy constraints. A closed-form solution for the optimal power allocation between the source and the relay can be obtained by the Karush-Kuhn-Tucker (KKT) conditions. Furthermore, simulation results and comparisons are presented to illustrate the performance of the proposed scheme.